New Study Links Common Viral Illnesses to Six Brain Diseases

The scientists say their results don’t prove viral infections cause diseases such as Alzheimer’s and dementia. Instead, their findings offer more insight into the possible connections between viruses and neurodegenerative disorders.

Studies have already found links between influenza and Parkinson’s disease (PD), and human papillomavirus and dementia. Most recently, researchers examining the records of 10 million US soldiers uncovered a link between the Epstein-Barr virus and multiple sclerosis (MS).

Inspired by that discovery and the growing concern about the neurological ramifications of the virus that causes COVID-19, researchers from the National Institutes of Health (NIH) decided to investigate the potential links between viral exposures and neurodegenerative disease risk.

Their research appears in the journal Neuron.

The scientists analyzed over 400,000 data samples from FinnGen and the UK Biobank — two large national biobanks in Finland and the United Kingdom.

They looked for an association between viral infections and Alzheimer’s disease (AD), generalized dementia (DEM), vascular dementia (VAS), Parkinson’s disease (PD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS) — also known as Lou Gehrig’s disease.

Some of the viruses included in the investigation were influenza, viral encephalitis, viral and other specified intestinal infections, and varicella-zoster virus.

Using the FinnGen data, the team identified 45 viral illnesses significantly associated with an increased risk of neurodegenerative disease. They also replicated 22 of these associations in the UK Biobank data.

After further analysis, the scientists found a significant association between viral encephalitis exposure and Alzheimer’s disease. In addition, influenza and pneumonia were significantly associated with five of the six neurodegenerative diseases examined. These include ALS, AD, PD, VAS, and dementia.

The data analysis also revealed that viral encephalitis and viral and other specified intestinal infections were associated with AD and dementia. The team also found an association between the varicella-zoster virus and MS and VAS.

What’s more, some of these illnesses were associated with an increased risk of neurodegenerative diseases up to 15 years after infection.

Additionally, the team also found the same Epstein-Barr/MS associations previously observed in the US soldier study.

According to the study, all the viruses examined were associated with an increased risk of neurodegenerative disease. In addition, many of these viruses cross the blood-brain barrier and invade the nervous system. Therefore, the researchers suggest that these viruses may increase the risk of neurodegenerative disease by contributing to brain inflammation.

Still, the study has weaknesses. Specifically, it does not prove that these viruses cause neurodegenerative disease. In addition, the data used for the research was based on billing codes and not bloodwork or other tests.

However, the study authors suggest that their findings warrant further investigations into the associations between viral illness and neurodegenerative diseases. They also say more research is needed to determine if vaccinations or antiviral medications might play a role in preventing these brain disorders.

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